Process for removing metals from resid

ABSTRACT

A process for removing a metal from a resid feed includes contacting the resid feed comprising the metal with a resid-immiscible ionic liquid to produce a resid and resid-immiscible ionic liquid mixture, and separating the mixture to produce a resid effluent having a reduced metal content relative to the resid feed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/291,295 filed Dec. 30, 2009.

FIELD OF THE INVENTION

The present invention relates to processes for removing one or moremetals from petroleum resid. More particularly, the invention relates tosuch processes using an ionic liquid.

BACKGROUND OF THE INVENTION

Petroleum resid is the bottoms or heavy fraction produced by distillingpetroleum crudes and may be referred to as atmospheric resid and vacuumresid to indicate the type of distillation. Resid may be converted intotransportation fuels such as jet, diesel, and gasoline by a variety ofprocesses. However, the metal content of the resid, e.g., alkali,alkaline earth metals, first transition metals, as well as Al, Sn, Pb,Sb, and the like may poison the catalysts used and cause higher cokeproduction, which can decrease the conversion and/or selectivity of thevarious processes employed.

Conventionally, the resid metal content may be concentrated in a coke orbottoms product of thermal processes such as coking and visbreaking,which also produce lighter hydrocarbon fractions such as naphtha,diesel. Although the metals are concentrated in the heavier products inthese thermal processes, the lighter products may require additional orspecialized processing because they contain significantly more metalsrelative to similar boiling range straight run fractions. Metals inresid may also be removed by adsorption onto solid particles such ascatalysts or adsorbents. Such particles may be used in conjunction withresid hydrotreating processes that also reduce the nitrogen and sulfurcontent of the resid.

Various processes using ionic liquids to remove sulfur and nitrogencompounds from hydrocarbon fractions are known. U.S. Pat. No. 7,001,504B2 discloses a process for the removal of organosulfur compounds fromhydrocarbon materials which includes contacting an ionic liquid with ahydrocarbon material to extract sulfur containing compounds into theionic liquid. U.S. Pat. No. 7,553,406 B2 discloses a process forremoving polarizable impurities from hydrocarbons and mixtures ofhydrocarbons using ionic liquids as an extraction medium. U.S. Pat. No.7,553,406 B2 also discloses that different ionic liquids show differentextractive properties for different polarizable compounds.

Liquid/Liquid Extraction of Metal Ions in Room Temperature IonicLiquids, by Visser, Ann E., et al, SEPARATION SCIENCE AND TECHNOLOGY,36(5&6), 785-804, (2001), Marcel Dekker, Inc., discloses the use of roomtemperature ionic liquids, specifically, 1-alkyl-3-methylimidazoliumhexafluorophosphate, to separate metal ions from aqueous solutions.

There remains a need in the art for improved processes that reduce themetal content of petroleum resid.

SUMMARY OF THE INVENTION

In an embodiment, the invention is a process for removing a metal from aresid comprising: contacting the resid comprising the metal with aresid-immiscible ionic liquid comprising at least one of an imidazoliumionic liquid, a pyridinium ionic liquid, an ammonium ionic liquid, and aphosphonium ionic liquid to produce a mixture comprising the resid andthe resid-immiscible ionic liquid; and separating the mixture to producea resid effluent and a resid-immiscible ionic liquid effluent comprisingthe metal.

In another embodiment, the resid-immiscible ionic liquid comprises atleast one of 1-butyl-3-methylimidazolium hexafluorophosphate,1-ethyl-3-methylimidazolium ethyl sulfate, methylimidazoliumtrifluoroacetate, 1-butyl-3-methylimidazolium bromide,1-butyl-3-methylimidazolium hydrogen sulfate, pyridinium p-toluenesulfonate, 1-ethyl-3-methylimidazolium trifluoroacetate,1-ethyl-3-methylimidazolium chloride, tetraethyl-ammonium acetate,tetrabutylphosphonium methanesulfonate, 1-methylimidazolium hydrogensulfate, and 1-butylpyridinium chloride.

In a further embodiment, the mixture comprises water in an amount lessthan 10% relative to the amount of resid-immiscible ionic liquid in themixture on a weight basis; the mixture may be water free.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified flow scheme illustrating various embodiments ofthe invention.

FIGS. 2A and 2B are simplified flow schemes illustrating differentembodiments of an extraction zone of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In general, the invention may be used to remove one or more metals fromresid through use of a resid-immiscible ionic liquid.

The term “resid” as used herein is to be interpreted broadly to receivenot only its ordinary meanings as used by those skilled in the art ofproducing and converting such hydrocarbon fractions, but also in a broadmanner to account for the application of our processes to hydrocarbonfractions exhibiting resid-like characteristics. Thus, the termencompass atmospheric resid and vacuum resid as may be produced in acrude fractionation section of an oil refinery and from other processesthat may be used to separate crude oil into hydrocarbon fractions. Thecrude oil to be separated may be any full range crude oil produced froman oil field and/or any full range synthetic crude produced, forexample, from tar sand, bitumen, shale oil, and coal. Multiple crudeoils may be blended to produce the resid. The resid introduced toprocesses of this invention may be a blend or mixture of multipleresids.

In general, resid comprises a variety of hydrocarbon components boilingabove 600° C. and contains impurities such as sulfur, nitrogen andmetals. The sulfur level in resid may range from about 0.5 wt % to about5 wt %, the nitrogen level may range from about 0.05 wt % to about 3 wt%, and the total metals level may range from about 0.1 ppm-wt to about2000 ppm-wt. The concentration of nickel in resid may range from about0.01 ppm-wt to about 200 ppm-wt and the concentration of vanadium mayrange from about 0.1 ppm-wt to about 1500 ppm-wt. The nitrogen contentmay be determined using ASTM method D4629-02, Trace Nitrogen in LiquidPetroleum Hydrocarbons by Syringe/Inlet Oxidative Combustion andChemiluminescence Detection. The sulfur content may be determined usingASTM method D5453-00, Ultraviolet Fluorescence; and the metals contentmay be determined by UOP389-09, Trace Metals in Oils by Wet Ashing andICP-OES. Unless otherwise noted, the analytical methods used herein suchas ASTM D5453-00 and UOP389-09 are available from ASTM International,100 Barr Harbor Drive, West Conshohocken, Pa., USA.

Processes according to the invention reduce the metal content of aresid. The resid may comprise a plurality of metals in various amounts.Thus, the invention removes at least a portion of at least one metalfrom the resid. The invention may remove the same or different amountsof each type of metal, and some metals may not be removed. In anembodiment, the metal comprises at least one of an alkali metal, analkaline earth metal, a first transition metal, aluminum, tin, lead, andantimony. In another embodiment, the metal comprises at least one firsttransition metal and the metal may comprise at least one of nickel,vanadium, and iron. In a further embodiment, the metal is selected fromthe group consisting of an alkali metal, an alkaline earth metal, afirst transition metal, aluminum, tin, lead, antimony, and combinationsthereof. The metal may be selected from the group consisting of nickel,vanadium, iron, and combinations thereof.

In an embodiment, a metal content of the resid is reduced by at leastabout 10% on an elemental basis. The invention may remove at least about40% of a metal from the resid on an elemental basis; and the inventionmay remove at least about 60% of a metal from the resid on an elementalbasis. In another embodiment, an individual metal of the resid isreduced by at least about 10% on an elemental basis in a single metalremoval step. An individual metal of the resid may be reduced by atleast about 30% on an elemental basis in a single metal removal step;and an individual metal of the resid may be reduced by at least about50% on an elemental basis in a single metal removal step. In a furtherembodiment, the invention removes at least about 30% of the nickel andvanadium from the resid on a combined weight basis; and the inventionmay remove at least about 50% of the nickel and vanadium from the residon a combined weight basis. For example, the invention removes 40% ofthe nickel and vanadium from the resid on a combined weight basis if theresid feed contains 80 ppm-wt nickel and 120 ppm-wt vanadium and theresid effluent contains 20 ppm-wt nickel and 100 ppm-wt vanadium. Themetal removed may be part of a hydrocarbon molecule or complexed with ahydrocarbon molecule.

One or more ionic liquids may be used to extract one or more metals fromresid. Generally, ionic liquids are non-aqueous, organic salts composedof ions where the positive ion is charge balanced with negative ion.These materials have low melting points, often below 100° C.,undetectable vapor pressure and good chemical and thermal stability. Thecationic charge of the salt is localized over hetero atoms, such asnitrogen, phosphorous, sulfur, arsenic, boron, antimony, and aluminum,and the anions may be any inorganic, organic, or organometallic species.

Ionic liquids suitable for use in the instant invention areresid-immiscible ionic liquids. As used herein the term“resid-immiscible ionic liquid” means the ionic liquid is capable offorming a separate phase from resid under operating conditions of theprocess. Ionic liquids that are miscible with resid at the processconditions will be completely soluble with the resid; therefore, nophase separation would be feasible. Thus, resid-immiscible ionic liquidsmay be insoluble with or partially soluble with resid under operatingconditions. An ionic liquid capable of forming a separate phase from theresid under the operating conditions is considered to beresid-immiscible. Ionic liquids according to the invention may beinsoluble, partially soluble, or completely soluble (miscible) withwater.

In an embodiment, the resid-immiscible ionic liquid comprises at leastone of an imidazolium ionic liquid, a pyridinium ionic liquid, anammonium ionic liquid, and a phosphonium ionic liquid. In anotherembodiment, the resid-immiscible ionic liquid is selected from the groupconsisting of imidazolium ionic liquids, pyridinium ionic liquids,ammonium ionic liquids, phosphonium ionic liquids and combinationsthereof. Imidazolium, pyridinium and ammonium ionic liquids have acation comprising at least one nitrogen atom. Phosphonium ionic liquidshave a cation comprising at least one phosphorus atom. In an embodiment,the resid-immiscible ionic liquid comprises at least one of1-butyl-3-methylimidazolium hexafluorophosphate,1-ethyl-3-methylimidazolium ethyl sulfate, methylimidazoliumtrifluoroacetate, 1-butyl-3-methylimidazolium bromide,1-butyl-3-methylimidazolium hydrogen sulfate, pyridinium p-toluenesulfonate, 1-ethyl-3-methylimidazolium trifluoroacetate,1-ethyl-3-methylimidazolium chloride, tetraethyl-ammonium acetate,tetrabutylphosphonium methanesulfonate, 1-methylimidazolium hydrogensulfate, and 1-butylpyridinium chloride. The resid-immiscible ionicliquid may be selected from the group consisting of1-butyl-3-methylimidazolium hexafluorophosphate,1-ethyl-3-methylimidazolium ethyl sulfate, methylimidazoliumtrifluoroacetate, 1-butyl-3-methylimidazolium bromide,1-butyl-3-methylimidazolium hydrogen sulfate, pyridinium p-toluenesulfonate, 1-ethyl-3-methylimidazolium trifluoroacetate,1-ethyl-3-methylimidazolium chloride, tetraethyl-ammonium acetate,tetrabutylphosphonium methanesulfonate, 1-methylimidazolium hydrogensulfate, 1-butylpyridinium chloride, and combinations thereof.

In an embodiment, the invention is a process for removing a metal fromresid comprising a contacting step and a separating step. In thecontacting step, the resid comprising the metal and a resid-immiscibleionic liquid are contacted or mixed. The contacting may facilitatetransfer or extraction of the one or more metals from the resid to theionic liquid. Although a resid-immiscible ionic liquid that is partiallysoluble in resid may facilitate transfer of the metal from the resid tothe ionic liquid, partial solubility is not required. Insolubleresid/ionic liquid mixtures may have sufficient interfacial surface areabetween the resid and ionic liquid to be useful. In the separation step,the mixture of resid and ionic liquid settles or forms two phases, aresid phase and an ionic liquid phase, which are separated to produce aresid-immiscible ionic liquid effluent comprising the metal and a resideffluent.

The process may be conducted in various equipment which are well knownin the art and are suitable for batch or continuous operation. Forexample, in a small scale form of the invention, resid and aresid-immiscible ionic liquid may be mixed in a beaker, flask, or othervessel, e.g. by stirring, shaking, use of a mixer, or a magneticstirrer. The mixing or agitation is stopped and the mixture forms aresid phase and an ionic liquid phase which can be separated, forexample, by decanting or use of a pipette to produce a resid effluenthaving a lower metal content relative to the resid. The process alsoproduces a resid-immiscible ionic liquid effluent comprising the metal.

The contacting and separating steps may be repeated for example when themetal content of the resid effluent is to be reduced further to obtain adesired metal level in the ultimate resid product stream from theprocess. Each set, group, or pair of contacting and separating steps maybe referred to as a metal removal step. Thus, the invention encompassessingle and multiple metal removal steps. A metal removal zone may beused to perform a metal removal step. As used herein, the term “zone”can refer to one or more equipment items and/or one or more sub-zones.Equipment items may include, for example, one or more vessels, heaters,separators, exchangers, conduits, pumps, compressors, and controllers.Additionally, an equipment item can further include one or more zones orsub-zones. The metal removal process or step may be conducted in asimilar manner and with similar equipment as is used to conduct otherliquid-liquid wash and extraction operations. Suitable equipmentincludes, for example, columns with: trays, packing, rotating discs orplates, and static mixers. Pulse columns and mixing/settling tanks mayalso be used.

FIG. 2A illustrates an embodiment of the invention which may bepracticed in metal removal or extraction zone 100 that comprises amulti-stage, counter-current extraction column 105 wherein resid andresid-immiscible ionic liquid are contacted and separated. The resid orresid feed stream 2 enters extraction column 105 through resid feedinlet 102 and lean ionic liquid stream 4 enters extraction column 105through ionic liquid inlet 104. In the Figures, reference numerals ofthe streams and the lines or conduits in which they flow are the same.Resid feed inlet 102 is located below ionic liquid inlet 104. The resideffluent passes through resid effluent outlet 112 in an upper portion ofextraction column 105 to resid effluent conduit 6. The resid-immiscibleionic liquid effluent including the metals removed from the resid feedpasses through ionic liquid effluent outlet 114 in a lower portion ofextraction column 105 to ionic liquid effluent conduit 8.

Consistent with common terms of art, the ionic liquid introduced to themetal removal step may be referred to as a “lean ionic liquid” generallymeaning a resid-immiscible ionic liquid that is not saturated with oneor more extracted metals. Lean ionic liquid may include one or both offresh and regenerated ionic liquid and is suitable for accepting orextracting metal from the resid feed. Likewise, the ionic liquideffluent may be referred to as “rich ionic liquid”, which generallymeans a resid-immiscible ionic liquid effluent produced by a metalremoval step or process or otherwise including a greater amount ofextracted metals than the amount of extracted metals included in thelean ionic liquid. A rich ionic liquid may require regeneration ordilution, e.g. with fresh ionic liquid, before recycling the rich ionicliquid to the same or another metal removal step of the process.

FIG. 2B illustrates another embodiment of metal removal washing zone 100that comprises a contacting zone 200 and a separation zone 300. In thisembodiment, lean ionic liquid stream 4 and resid feed stream 2 areintroduced into the contacting zone 200 and mixed by introducing residfeed stream 2 into the flowing lean ionic liquid stream 4 and passingthe combined streams through static in-line mixer 155. Static in-linemixers are well known in the art and may include a conduit with fixedinternals such as baffles, fins, and channels that mix the fluid as itflows through the conduit. In other embodiments, not illustrated, leanionic liquid stream 4 may be introduced into resid feed stream 2, or thelean ionic liquid stream 4 and resid feed stream may be combined such asthrough a “Y” conduit. In another embodiment, lean ionic liquid stream 4and resid feed stream 2 are separately introduced into the staticin-line mixer 155. In other embodiments, the streams may be mixed by anymethod well know in the art including stirred tank and blendingoperations. The mixture comprising resid and ionic liquid is transferredto separation zone 300 via transfer conduit 7. Separation zone 300comprises separation vessel 165 wherein the two phases are allowed toseparate into a rich ionic liquid phase which is withdrawn from a lowerportion of separation vessel 165 via ionic liquid effluent conduit 8 andthe resid phase is withdrawn from an upper portion of separation vessel165 via resid effluent conduit 6. Separation vessel 165 may comprise aboot, not illustrated, from which rich ionic liquid is withdrawn viaconduit 8.

Separation vessel 165 may contain a solid media 175 and/or othercoalescing devices which facilitate the phase separation. In otherembodiments the separation zone 300 may comprise multiple vessels whichmay be arranged in series, parallel, or a combination thereof. Theseparation vessels may be of any shape and configuration to facilitatethe separation, collection, and removal of the two phases. In a furtherembodiment, metal removal zone 100 may include a single vessel whereinlean ionic liquid stream 4 and resid feed stream 2 are mixed, thenremain in the vessel to settle into the resid effluent and rich ionicliquid phases. In an embodiment the process comprises at least two metalremoval steps. For example, the resid effluent from one metal removalstep may be passed directly as the resid feed to a second metal removalstep. In another embodiment, the resid effluent from one metal removalstep may be treated or processed before being introduced as the residfeed to the second metal removal step. There is no requirement that eachmetal removal zone comprises the same type of equipment. Differentequipment and conditions may be used in different metal removal zones.

The metal removal step may be conducted under metal removal conditionsincluding temperatures and pressures sufficient to keep theresid-immiscible ionic liquid and resid feeds and effluents as liquids.For example, the metal removal step temperature may range between about10° C. and less than the decomposition temperature of the ionic liquid,usually less than about 300° C.; and the pressure may range betweenabout atmospheric pressure and about 700 kPa(g). When theresid-immiscible ionic liquid comprises more than one ionic liquidcomponent, the decomposition temperature of the ionic liquid is thelowest temperature at which any of the ionic liquid componentsdecompose. The metal removal step may be conducted at a uniformtemperature and pressure or the contacting and separating steps of themetal removal step may be operated at different temperatures and/orpressures. In an embodiment, the contacting step is conducted at a firsttemperature, and the separating step is conducted at a temperature atleast 5° C. lower than the first temperature. In a non limiting examplethe first temperature is about 80° C. Such temperature differences mayfacilitate separation of the resid and ionic liquid phases.

The above and other metal removal step conditions such as the contactingor mixing time, the separation or settling time, and the ratio of residfeed to resid-immiscible ionic liquid (lean ionic liquid) may varygreatly based, for example, on the specific ionic liquid or liquidsemployed, the nature of the resid feed, the metal content of the residfeed, the degree of metal removal required, the number of metal removalsteps employed, and the specific equipment used. In general it isexpected that contacting time may range from less than one minute toabout two hours; settling time may range from about one minute to abouteight hours; and the weight ratio of resid feed to lean ionic liquidintroduced to the metal removal step may range from 1:10,000 to10,000:1. In an embodiment, the weight ratio of resid feed to lean ionicliquid may range from about 1:1,000 to about 1,000:1; and the weightratio of resid feed to lean ionic liquid may range from about 1:100 toabout 100:1. In an embodiment the weight of resid is greater than theweight of ionic liquid introduced to the metal removal step. The degreeof phase separation between the resid and ionic liquid phases is anotherfactor to consider as it affects recovery of the ionic liquid and resid.The degree of metal removed and the recovery of the resid and ionicliquids may be affected differently by the nature of the resid feed, thespecific ionic liquid or liquids, the equipment, and the metal removalconditions such as those discussed above.

The amount of water present in the resid/resid-immiscible ionic liquidmixture during the metal removal step may also affect the amount ofmetal removed and/or the degree of phase separation, i.e. recovery ofthe resid and ionic liquid. In an embodiment, the resid/resid-immiscibleionic liquid mixture has a water content of less than about 10% relativeto the weight of the ionic liquid. In another embodiment, the watercontent of the resid/resid-immiscible ionic liquid mixture is less thanabout 5% relative to the weight of the ionic liquid; and the watercontent of the resid/resid-immiscible ionic liquid mixture may be lessthan about 2% relative to the weight of the ionic liquid. In a furtherembodiment, the resid/resid-immiscible ionic liquid mixture is waterfree, i.e. the mixture does not contain water.

FIG. 1 is a flow scheme illustrating various embodiments of theinvention and some of the optional and/or alternate steps and apparatusencompassed by the invention. Resid stream 2 and resid-immiscible ionicliquid stream 4 are introduced to and contacted and separated in metalremoval zone 100 to produce resid-immiscible ionic liquid effluentstream 8 and resid effluent stream 6 as described above. The ionicliquid stream 4 may be comprised of fresh ionic liquid stream 3 and/orone or more ionic liquid streams which are recycled in the process asdescribed below. In an embodiment, a portion or all of resid effluentstream 6 is passed via conduit 10 to a hydrocarbon conversion zone 800.Hydrocarbon conversion zone 800 may, for example, comprise at least oneof a deasphalting, visbreaking, hydrocracking, and coking process whichare well known in the art.

An optional resid washing step may be used, for example, to recoverionic liquid that is entrained or otherwise remains in the resideffluent stream by using water to wash or extract the ionic liquid fromthe resid effluent. In this embodiment, a portion or all of resideffluent stream 6 (as feed) and a water stream 12 (as solvent) areintroduced to resid washing zone 400. The resid effluent and waterstreams introduced to resid washing zone 400 are mixed and separated toproduce a washed resid stream 14 and a spent water stream 16, whichcomprises the ionic liquid. The resid washing step may be conducted in asimilar manner and with similar equipment as used to conduct otherliquid-liquid wash and extraction operations as discussed above. Variousresid washing step equipment and conditions such as temperature,pressure, times, and solvent to feed ratio may be the same as ordifferent from the metal removal zone equipment and conditions. Ingeneral, the resid washing step conditions will fall within the sameranges as given above for the metal removal step conditions. A portionor all of the washed resid stream 14 may be passed to hydrocarbonconversion zone 800.

An optional ionic liquid regeneration step may be used, for example, toregenerate the ionic liquid by removing the metal from the ionic liquid,i.e. reducing the metal content of the rich ionic liquid. In anembodiment, a portion or all of resid-immiscible ionic liquid effluentstream 8 (as feed) comprising the metal and a regeneration solventstream 18 are introduced to ionic liquid regeneration zone 500. Theresid-immiscible ionic liquid effluent and regeneration solvent streamsare mixed and separated to produce an extract stream 20 comprising themetal, and a regenerated ionic liquid stream 22. The ionic liquidregeneration step may be conducted in a similar manner and with similarequipment as used to conduct other liquid-liquid wash and extractionoperations as discussed above. Various ionic liquid regeneration stepconditions such as temperature, pressure, times, and solvent to feed maybe the same as or different from the metal removal conditions. Ingeneral, the ionic liquid regeneration step conditions will fall withinthe same ranges as given above for the metal removal step conditions.

In an embodiment, the regeneration solvent stream 18 comprises ahydrocarbon fraction lighter than resid and which is immiscible with theresid-immiscible ionic liquid. The lighter hydrocarbon fraction mayconsist of a single hydrocarbon compound or may comprise a mixture ofhydrocarbons. In an embodiment, the lighter hydrocarbon fractioncomprises at least one of a naphtha, gasoline, diesel, light cycle oil(LCO), and light coker gas oil (LCGO) hydrocarbon fraction. The lighterhydrocarbon fraction may comprise straight run fractions and/or productsfrom conversion processes such as hydrocracking, hydrotreating, fluidcatalytic cracking (FCC), reforming, coking, and visbreaking. In thisembodiment, extract stream 20 comprises the lighter hydrocarbonregeneration solvent and the metal. In another embodiment, theregeneration solvent stream 18 comprises water and the ionic liquidregeneration step produces extract stream 20 comprising the metal andregenerated resid-immiscible ionic liquid 22 comprising water and theionic liquid. In an embodiment wherein regeneration solvent stream 18comprises water, a portion or all of spent water stream 16 may provide aportion or all of regeneration solvent stream 18. Regardless of whetherregeneration solvent stream 18 comprises a lighter hydrocarbon fractionor water, a portion or all of regenerated resid-immiscible ionic liquidstream 22 may be recycled to the metal removal step via a conduit notshown consistent with other operating conditions of the process. Forexample, a constraint on the water content of the resid-immiscible ionicliquid stream 4 or ionic liquid/resid mixture in metal removal zone 100may be met by controlling the proportion and water content of fresh andrecycled ionic liquid streams.

Optional ionic liquid drying step is illustrated by drying zone 600. Theionic liquid drying step may be employed to reduce the water content ofone or more of the streams comprising ionic liquid to control the watercontent of the metal removal step as described above. In the embodimentof FIG. 1, a portion or all of regenerated resid-immiscible ionic liquidstream 22 is introduced to drying zone 600. Although not shown, otherstreams comprising ionic liquid such as the fresh ionic liquid stream 3,resid-immiscible ionic liquid effluent stream 8, and spent water stream16, may also be dried in any combination in drying zone 600. To dry theionic liquid stream or streams, water may be removed by one or morevarious well known methods including distillation, flash distillation,and using a dry inert gas to strip water. Generally, the dryingtemperature may range from about 100° C. to less than the decompositiontemperature of the ionic liquid, usually less than about 300° C. Thepressure may range from about 35 kPa(g) to about 250 kPa(g). The dryingstep produces a dried resid-immiscible ionic liquid stream 24 and adrying zone water effluent stream 26. Although not illustrated, aportion or all of dried resid-immiscible ionic liquid stream 24 may berecycled or passed to provide all or a portion of the resid-immiscibleionic liquid introduced to metal removal zone 100. A portion or all ofdrying zone water effluent stream 26 may be recycled or passed toprovide all or a portion of the water introduced into resid washing zone400 and/or ionic liquid regeneration zone 500.

Unless otherwise stated, the exact connection point of various inlet andeffluent streams within the zones is not essential to the invention. Forexample, it is well known in the art that a stream to a distillationzone may be sent directly to the column, or the stream may first be sentto other equipment within the zone such as heat exchangers, to adjusttemperature, and/or pumps to adjust the pressure. Likewise, streamsentering and leaving metal removal, washing, and regeneration zones maypass through ancillary equipment such as heat exchanges within thezones. Streams, including recycle streams, introduced to washing orextraction zones may be introduced individually or combined prior to orwithin such zones.

The invention encompasses a variety of flow scheme embodiments includingoptional destinations of streams, splitting streams to send the samecomposition, i.e. aliquot portions, to more than one destination, andrecycling various streams within the process. Examples include: variousstreams comprising ionic liquid and water may be dried and/or passed toother zones to provide all or a portion of the water and/or ionic liquidrequired by the destination zone. The various process steps may beoperated continuously and/or intermittently as needed for a givenembodiment e.g. based on the quantities and properties of the streams tobe processed in such steps. As discussed above the invention encompassesmultiple metal removal steps, which may be performed in parallel,sequentially, or a combination thereof. Multiple metal removal steps maybe performed within the same metal removal zone and/or multiple metalremoval zones may be employed with or without intervening washing,regeneration and/or drying zones.

EXAMPLES

The examples are presented to further illustrate some aspects andbenefits of the invention and are not to be considered as limiting thescope of the invention.

Example 1

A commercial sample of a vacuum resid with the properties listed inTable 1 was obtained for use a feed stream. The nitrogen content wasdetermined by ASTM Method D4629-02, Trace Nitrogen in Liquid PetroleumHydrocarbons by Syringe/Inlet Oxidative Combustion and ChemiluminescenceDetection. The sulfur content was determined by ASTM Method D5453-00,Ultraviolet Fluorescence. The metals content was determined byUOP389-09, Trace Metals in Oils by Wet Ashing and ICP-OES.

TABLE 1 Sulfur, wt % 4.0 Nitrogen, ppm-wt 6,000 Nickel, ppm-wt 68Vanadium, ppm-wt 220 Iron, ppm-wt 15 API 5.9

Examples 2-10

The resid of Example 1 and the ionic liquid listed in Table 2 were mixedovernight in the ratios given in Table 2 at 150° C. using a digitalmagnetic stirrer hot plate. After mixing was stopped, the samples wereheld static at 80° C. for 30 minutes then a sample of the resid phase(resid effluent) was removed with a pipette and analyzed for metals. Theresults are compared in Table 2 where the amounts of metal removed fromthe resid are reported as a percentage on an elemental basis. In Table 2a result of zero (“0”) means none of that metal was removed while “NA”means the sample was not analyzed.

TABLE 2 Resid to IL weight Vanadium Nickel Iron Example Ionic Liquid(IL) ratio removed, % removed, % removed, % 2 1-butyl-3- 1:1   40 34 0methylimidazolium hexafluorophosphate 3 1-ethyl-3- 1:0.5 0 0 0methylimidazolium chloride 4 1-ethyl-3- 1:1   23 24 0 methylimidazoliumethyl sulfate 5 tetraethyl-ammonium 1:0.5 0 0 0 acetate 6 pyridiniumtrifluoro 1:0.5 0 0 90 acetate 7 1-methylimidazolium 1:0.5 52 51 45trifluoroacetate 8 1-butyl-3- 1:0.5 11 10 27 methylimidazolium bromide 91-butyl-3- 1:1   0 0 21 methylimidazolium hydrogen sulfate 10 pyridiniump-toluene 1:1   36 35 NA sulfonate

Examples 11-16

The resid of Example 1 and the ionic liquid listed in Table 3 were mixedfor 2 hours at 120° C. in a weight ratio resid to ionic liquid of 2:1using an automated mixing device with an overhead impeller. After mixingwas stopped, the samples were centrifuged at 300 rpm for 30 minutes thena sample of the resid phase (resid effluent) was removed with a pipetteand analyzed for metals. The results are compared in Table 3 where theamounts of metal removed from the resid are reported as a percentage onan elemental basis. In Table 3 a result of zero (“0”) means none of thatmetal was removed.

TABLE 3 Vanadium Nickel removed, removed, Example Ionic Liquid (IL) % %11 1-ethyl-3-methylimidazolium 21 21 trifluoroacetate 121-ethyl-3-methylimidazolium chloride 22 0 13 tetraethyl-ammonium acetate19 1 14 tetrabutylphosphonium 26 20 methanesulfonate 151-methylimidazolium hydrogen 24 0 sulfate 16 1-butylpyridinium chloride20 8

Examples 2-16 illustrate that a resid-immiscible ionic liquid comprisingat least one of an imidazolium ionic liquid, a pyridinium ionic liquid,an ammonium ionic liquid, and a phosphonium ionic liquid removes metal,e.g. at least one of vanadium, nickel, and iron from resid. The resultsalso demonstrate the unpredictable nature of this art as the resultsvary significantly between the metals, the groups of ionic liquids, andwithin a group of similar ionic liquids.

The invention claimed is:
 1. A process for removing a metal from a residcomprising: (a) contacting the resid comprising the metal with aresid-immiscible ionic liquid to produce a mixture comprising the residand the resid-immiscible ionic liquid, the resid-immiscible ionic liquidcomprising at least one of an imidazolium ionic liquid, a pyridiniumionic liquid, an ammonium ionic liquid, and a phosphonium ionic liquid;and (b) separating the mixture to produce a resid effluent and aresid-immiscible ionic liquid effluent, the resid-immiscible ionicliquid effluent comprising the metal; wherein the resid-immiscible ionicliquid comprises at least one of 1-butyl-3-methylimidazoliumhexafluorophosphate, 1-ethyl-3-methylimidazolium ethyl sulfate,methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide,1-butyl-3-methylimidazolium hydrogen sulfate, pyridinium p-toluenesulfonate, 1-ethyl-3-methylimidazolium trifluoroacetate,1-ethyl-3-methylimidazolium chloride, tetraethyl-ammonium acetate,tetrabutylphosphonium methanesulfonate, 1-methylimidazolium hydrogensulfate, and 1-butylpyridinium chloride; and wherein the metal contentof the resid is reduced by at least 10-60% on an elemental basis;wherein the resid effluent comprises resid-immiscible ionic liquid, theprocess further comprising washing at least a portion of the resideffluent with water to produce a washed resid stream and a spent waterstream, the spent water stream comprising the resid-immiscible ionicliquid; wherein at least a portion of the spent water stream is at leasta portion of the regeneration solvent; wherein the regeneration solventcomprises water and the regenerated resid-immiscible ionic liquid streamcomprises water and wherein the process further comprises contacting theresid-immiscible ionic liquid effluent with a regeneration solvent andseparating the resid-immiscible ionic liquid effluent from theregeneration solvent to produce an extract stream comprising the metaland a regenerated resid-immiscible ionic liquid stream.
 2. The processof claim 1 further comprising drying at least a portion of at least oneof the regenerated resid-immiscible ionic liquid stream, and the spentwater stream to produce a dried resid-immiscible ionic liquid stream. 3.The process of claim 2 further comprising recycling at least a portionof the dried resid-immiscible ionic liquid stream to the metal removalcontacting step.
 4. A process for removing a metal from a residcomprising: (a) contacting the resid comprising the metal with aresid-immiscible ionic liquid to produce a mixture comprising the resid,and the resid-immiscible ionic liquid, the resid-immiscible ionic liquidcomprising at least one of an imidazolium ionic liquid, a pyridiniumionic liquid, an ammonium ionic liquid, and a phosphonium ionic liquid;(b) separating the mixture to produce a resid effluent and aresid-immiscible ionic liquid effluent, the resid-immiscible ionicliquid effluent comprising the metal; and at least one of: (c) washingat least a portion of the resid effluent with water to produce a washedresid stream and a spent water stream; (d) contacting theresid-immiscible ionic liquid effluent with a regeneration solvent andseparating the resid-immiscible ionic liquid effluent from theregeneration solvent to produce an extract stream comprising the metaland a regenerated resid-immiscible ionic liquid stream; and (e) dryingat least a portion of at least one of the resid-immiscible ionic liquideffluent, the spent water stream, and the regenerated resid-immiscibleionic liquid stream to produce a dried resid-immiscible ionic liquidstream.
 5. The process of claim 4 further comprising recycling at leasta portion of at least one of the resid-immiscible ionic liquid effluent,the spent water stream, the regenerated resid-immiscible ionic liquidstream, and the dried resid-immiscible ionic liquid stream to the metalremoval contacting step.